The diploma thesis deals with the detection of measurement error based on the question order using the reaction time. The major part of the theoretical chapter deals with the respondent as the source of the error. A respondent needs to proceed through a cognitive process to answer a question. Various influences affect the process and they might have an effect on the accuracy of the answer. The frequently mentioned effects are age, education and motivation of respondent. The absence of respondents' motivation might lead to a reduction of their effort to properly proceed with the cognitive process. In that case, the respondent does not dedicate the appropriate cognitive effort and time to a question in the questionnaire. That length of time, which the respondent takes to answer, is called the reaction time and it is suggested that it might be used as an indicator of the amount of cognitive effort. Based on previously executed studies, the author designed hypotheses about the change in length of the reaction time with a change of question position in a questionnaire, about the effect of respondents' characteristics on the reaction time and its shortening. The significant shortening of the reaction time on the question located closer to the end of the experimental questionnaire is used as an indicator...